<?php declare(strict_types=1);
/**
 * @author      xianganyall <xianganyall@gmail.com>
 * @copyright   2023-2025 owner
 **/

namespace Srv\Libs\Plugins\QrCode;

class QrRsItem
{
    public int $mm;                  // Bits per symbol
    public int $nn;                  // Symbols per block (= (1<<mm)-1)
    public array $alpha_to = [];  // log lookup table
    public array $index_of = [];  // Antilog lookup table
    public array $genpoly = [];   // Generator polynomial
    public int $nroots;              // Number of generator roots = number of parity symbols
    public int $fcr;                 // First consecutive root, index form
    public int $prim;                // Primitive element, index formy
    public int $iprim;               // prim-th root of 1, index form
    public int $pad;                 // Padding bytes in shortened block
    public int $gfpoly;

    public function modnn($x)
    {
        while ($x >= $this->nn) {
            $x -= $this->nn;
            $x = ($x >> $this->mm) + ($x & $this->nn);
        }
        return $x;
    }

    public static function init_rs_char($symsize, $gfpoly, $fcr, $prim, $nroots, $pad): ?QrRsItem
    {
        if ($symsize < 0 || $symsize > 8) return null;
        if ($fcr < 0 || $fcr >= (1 << $symsize)) return null;
        if ($prim <= 0 || $prim >= (1 << $symsize)) return null;
        if ($nroots < 0 || $nroots >= (1 << $symsize)) return null; // Can't have more roots than symbol values!
        if ($pad < 0 || $pad >= ((1 << $symsize) - 1 - $nroots)) return null; // Too much padding
        $rs = new QrRsItem();
        $rs->mm = $symsize;
        $rs->nn = (1 << $symsize) - 1;
        $rs->pad = $pad;
        $rs->alpha_to = array_fill(0, $rs->nn + 1, 0);
        $rs->index_of = array_fill(0, $rs->nn + 1, 0);
        $NN = &$rs->nn;
        $A0 = &$NN;
        $rs->index_of[0] = $A0;
        $rs->alpha_to[$A0] = 0;
        $sr = 1;
        for ($i = 0; $i < $rs->nn; $i++) {
            $rs->index_of[$sr] = $i;
            $rs->alpha_to[$i] = $sr;
            $sr <<= 1;
            if ($sr & (1 << $symsize)) {
                $sr ^= $gfpoly;
            }
            $sr &= $rs->nn;
        }
        if ($sr != 1) return null;
        $rs->genpoly = array_fill(0, $nroots + 1, 0);
        $rs->fcr = $fcr;
        $rs->prim = $prim;
        $rs->nroots = $nroots;
        $rs->gfpoly = $gfpoly;
        $iprim = 1;
        while (($iprim % $prim) != 0) {
            $iprim += $rs->nn;
        }
        $rs->iprim = intval($iprim / $prim);
        $rs->genpoly[0] = 1;
        for ($i = 0, $root = $fcr * $prim; $i < $nroots; $i++, $root += $prim) {
            $rs->genpoly[$i + 1] = 1;
            for ($j = $i; $j > 0; $j--) {
                if ($rs->genpoly[$j] != 0) {
                    $rs->genpoly[$j] = $rs->genpoly[$j - 1] ^ $rs->alpha_to[$rs->modnn($rs->index_of[$rs->genpoly[$j]] + $root)];
                } else {
                    $rs->genpoly[$j] = $rs->genpoly[$j - 1];
                }
            }
            $rs->genpoly[0] = $rs->alpha_to[$rs->modnn($rs->index_of[$rs->genpoly[0]] + $root)];
        }
        for ($i = 0; $i <= $nroots; $i++) $rs->genpoly[$i] = $rs->index_of[$rs->genpoly[$i]];
        return $rs;
    }

    public function encode_rs_char($data, &$parity)
    {
        $NN = &$this->nn;
        $ALPHA_TO = &$this->alpha_to;
        $INDEX_OF = &$this->index_of;
        $GENPOLY = &$this->genpoly;
        $NROOTS = &$this->nroots;
        $PAD = &$this->pad;
        $A0 = &$NN;
        $parity = array_fill(0, $NROOTS, 0);
        for ($i = 0; $i < ($NN - $NROOTS - $PAD); $i++) {
            $feedback = $INDEX_OF[$data[$i] ^ $parity[0]];
            if ($feedback != $A0) {
                $feedback = $this->modnn($NN - $GENPOLY[$NROOTS] + $feedback);
                for ($j = 1; $j < $NROOTS; $j++) {
                    $parity[$j] ^= $ALPHA_TO[$this->modnn($feedback + $GENPOLY[$NROOTS - $j])];
                }
            }
            array_shift($parity);
            if ($feedback != $A0) {
                $parity[] = $ALPHA_TO[$this->modnn($feedback + $GENPOLY[0])];
            } else {
                $parity[] = 0;
            }
        }
    }
}